Apparatus for the manufacture of pipes and tubes



Dec. 24, 1935. B, BANNISTER APPARATUS FOR THE MANUFACTURE OF PIPES ANDTUBES 2 Sheets-Sheet 1 Filed March 15, 1933 BEY/QNT 54/v/w67-5,

Dec. 24, 1935. B. BANNISTER 7 2,025,148

APPARATUS FOR THE MANUFACTURE OF PIPES AND TUBES Filed March 15, 1933 2Sheets-Shet 2 V 34v PIEECING ELONGATING ZON E ZONEJ liweidow: BRYANT5,4'N/v/s TEE,

v diameter oi the rolls increases.

Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE APPARATUS FOR THEMANUFACTURE OF PIPES AND TUBES Bryant Bannister, Mount Lebanon, Pa.

Application March 15, 1933, Serial No. 660,967

3 Claims. (CI. 80-13) This invention relates to the manufacture ofseamless pipes and tubes from cast or rolled rounds and moreparticularly to a novel form of piercing mill for forming a hollow andrelatively thick-walled tube.

The usual piercing mill used for piercing a solid billet for subsequentrolling into seamless tubing of commercial dimensions operates to pierceand materially lengthen the solid billet without changing the diameterappreciably. This operation is performed by passing the sohd billetbetween a pair of power-rotated, obliquelydisposed barrel-shaped rollswhich rotate and torce the billet longitudinally over a conical mandrelor plug which is free to rotate but restricted Irom movinglongitudinally. The billet usually is maintained in proper positionbetween the main or reducing rolls by stationary guiding members locatedabove and below the billet.

These guiding members ofier considerable resistance to both rotationaland longitudinal movement of the billet. In some cases the guidingmembers are of an improved type consisting of a pair of power-rotatedguide rolls positioned intermediate the main rolls and with their midplanes substantially coincident with the longitudinal axis oi! the mill.These rolls have a peripheral speed in the direction of and greatly inexcess of the axial travel of the billet.

In my invention I employ power-rotated guide rolls in combination withmain rolls of the cone type to form a roll pass having a converging anda diverging section. The converging section is employed to grip thebillet and rotate it while advancing it forward into the mostconstricted portion of the pass, commonly termed the.

gorge. This necking down" or the billet produces a slight elongation andtends to cause the central fibers of the billet to open permitting theentry of the piercing point or plug. The diverging portion of the passincreases in width between the main rolls at the same rate as the Thusas the billet is pierced and passesv the gorge its diameter increasessubstantially at the same rate as the rolls increase in diameter. Thisarrangement provides that the peripheral speed of the billet and therolls is substantially the same for ceeding operations to be performedwith a minimum number of subsequent steps and abuse to the materialbeing formed into a tube. In producing tubes of small diameter it may bedesirable to secure an expansion in diameter without 5 a reduction ofcross-sectional area. in the expanding portion of the pass, but fortubes of large diameter and especially for those having relatively thinwalls it is desirable to obtain both a substantial increase in diameterand at the 10 same time an increase in length in the piercing mill. Theusual practice today in producing larger diameter pipe is to firstpierce a billet of considerably smaller diameter than the finished pipeto be produced and then expand this pierced l5 billet to greaterdiameter in a second operation.

The billet is then reduced in wall thickness and elongated to thedesired pipe size in subsequent operations. In my invention I obtain therequired increase in billet diameter in the pierc- 20 ing mill and, as aconsequence, I eliminate the usual second operation of expanding.

I take advantage of the natural tendency of the metal being pierced toflow most readily in a radial direction tending to produce a growth 25in the perimeter of the .pierced portion of the billet and I soproportion and position the piercing plug with respect to the main rollsthat the growth of perimeter or expansion of the billet proceeds withoutany material change in cross- 30 sectional area, and I also takeadvantage of the power-rotated guiding members by positioning them sothat they locate the billet in its proper position and assist the billetthrough the pass without materially restraining the expansion in 35diameter of the billet. It is obvious that so long as thecross-sectional area remains constant no elongation takes place. Aspreviously stated, it is usually desirable to secure in addition to anincrease in diameter a substantial increase in 40 length, and in myinvention I secure such increase by proportioning the piercing plug atits large end so that the distance between the plug and the main rollsdecreases at such a rate as to cause a reduction in cross-sectional areaof the billet, 4 thereby producing elongation. V This increased metaldisplacement tends to produce a rapid increase in billet diameter. Theguiding members are positioned so that their perimeters contact with thebillet intermediate the 50 main rolls in this portion of the pass andprevent the rapid increase in diameter, and owing to the high rate ofguide roll travel towards the outlet of the pass the potential increasein diameter is diverted into length.

It will be apparent to those skilled in the art that in order to causemetal of the billet to flow forwardly at a greater rate than the workrolls tend to impart in this direction, the metal must be free to flowor an upsetting action takes place. It is therefore desirable to locatethe elongating section of the pass in the outlet portion only where themetal displaced forwardly by the guide rolls is free to move in thisdirection without being retarded by metal that is restrained fromlongitudinal movement by the work roll grip.

It is an object of the invention to provide for obtaining a substantialpart of the increase in diameter of the work piece prior to obtainingelongation thereof. A further object of this invention is to provide aproduct which is free from sub-surface flaws sometimes present in tubesproduced by prior art practices.

These and other objects will appear after referring to the drawings, inwhich:

Figure 1 is an end elevation of the apparatus of my invention. a

Figure 2 is a plan view of my novel piercingpass lationship of one workroll to one of the guide rolls which is shown, together with a portionof the billet, in a plane substantially 90 degrees from its trueposition in the mill.

Figure 4 is a view similar to Figure 3 in which I have disclosed amodified form of my invention.

Referring more particularly to the drawings, in Figure 1 there isdisclosed an end elevation of the piercing mill of my invention. Thismill comprises a pair of conical working rolls 2 and powerdriven guiderolls 3 forming a roll pass surrounding the billet 4.

In Figure 2 of the drawings the point of the piercing plug 5 is shown aspositioned at the "gorge point of the working rolls 2. The positioningis nominal, as the plug may be given a lead or, in other words, extendinto the converging portion 2 of the work pass. A conical piercing plug5 is disposed in the interior of the billet 4 and is mounted on a bar 6for rotation therewith but is prevented from longitudinal movement.

Figure 3 of the drawings discloses a composite view showing therelationship of the various work and guide rolls to the piercing plugand the billet. As before stated, in this view the section of the guideroll 3 and portion of the billet 4 are shown in a plane substantiallydegrees from their true positions in the mill. The contour of thetapered piercing plug 5 is such that its relationship to the divergingportion 2 of the work pass will provide that the decrease in wallthickness is compensated for by an increase in workpiece diameter, sothat while the wall thickness is actually decreased the cross-sectionalareaof the wall is not reduced with the result that the work-piece doesnot increase substantially in longitudinal length throughout thisportion of the pass.

The work rolls are so proportioned that their surface speed bears asubstantially constant ratio to the surface speed of a billet at alltransverse sections of the expanding pass. In this form of the inventionit will be seen that prior to the introduction of the point of thepiercing plug the billet will be slightly elongated in the necking downwhich occurs in the converging portion 2 of the work pass but from'thispoint through to the outlet of the pass the pierced portion of Figure 3is a composite view disclosing the rethe billet, while being expanded ina substantial degree, will acquire no elongation.

Referring to Figure 4, I have shown in the view similar to Figure 3 amodified form of the invention in which the forward end of the piercingplug 5 provides for piercing and expanding with constant cross-sectionalarea, and the rearward portion of the said plug is so proportioned thatthe crosssectional area tends to produce a rapid increase in billetdiameter but the guide rolls 3 contact with the billet in this sectionof the pass and, because of their high rate of travel towards the outletof the pass and contact with the metal of the billet, divert thispotential increase in diameter into length. The work' rolls shown in 15Figure 4 have the same speed relationship through the outlet portion ofthe pass heretofore mentioned.

It will, of course, be obvious to those skilled in the art that thereducing section of the piercing plug 5 may be extended towards thepoint of the plug any desired amount w th corresponding reduction in thezone wherein constant crosssectional area is maintained. In the extreme,the elongating zone might be extended from the point of the plug to theoutlet of the pass, which will accomplish a constant elongation. Inpracticing this form of my invention it will readily follow that theguide rolls should contact the billet throughout the entire elongatingzone.

From the foregoing description, it will be noted that there is nopushing or crowding of the metal of the work-piece into and through thegorge, or constricted portion of the pass, such as would tend to fold,crease, or buckle the metal so pushed or 35 crowded. Inasmuch as theguide rolls 3 contact, the work-piece at the outlet side of the gorge orconstricted portion of the pass only, there is no straightening out offolded, creased, or buckled metal; and therefore the finished tube hasno 40 fibers which are fractured or pulled-apart and consequently thereare no sub-surface flaws, such as are present in the products of priorart practices where there is a pushing and crowding of the metal of thework-piece into and through 45 the gorge or constricted portion of thepass.

The term elongation in the claims is to be understood to mean thatoccurring in the diverging portion of the pass, and is not to beconstrued as defining the elongation which necessarily takes 50 place inthe necking down of the billet.

While I have shown and described several speci'fic embodiments of myinvention it willbe understood that I do not wish to be limited exactlythereto, since various modifications may be made 55 without departingfrom the scope of my invention, as defined in the following claims.

I claim:

1. Apparatus for piercing and expanding solid blanks comprising aplurality of metal working 0 rolls defining a pass including a gorgepoint adjacent its introductory end, in combination with at least onepower-actuated guide roll disposed intermediate said metal workingrolls, said guide roll being of a width substantially greater than 5 thediameter of the gorge of the pass and positioned to make initial contactwith the work piece at a point between the gorge and the outlet end atleast one power-actuated guide roll disposed intermediate said metalworking rolls, said guide roll being 01 a width substantially greaterthan the diameter or the gorge of the pass and positioned to makeinitial contact with the work piece at a point between the gorge and theoutlet end of the pass, whereby the contact or said guide roll isextended to the extreme outlet and of the wall reducing portion of saidpass.

3. Apparatus for the manufacture of pipes and tubes comprising aplurality of helically-actin power-driven metal-working .rolls, saidmetalworking rolls defining a metal-pass which is constrictedintermediate its ends, in combination metal-pass, said guide roll beingso positioned that its eflfective contact area is disposed entirelybetween the constrictedfportion 0t said metalpass and the outlet endthereof and extends to the outlet end or the wall reducing portion orthe pass.

BRYANT BANNISTER.

